The Static Physician’s Global Assessment of Genitalia: A Clinical Outcome Measure for the Severity of Genital Psoriasis

August 2017 | Volume 16 | Issue 8 | Original Article | 793 | Copyright © August 2017

Joseph F. Merola MD MMSc,a Alison Potts Bleakman PhD,b Alice B. Gottlieb MD PhD,c Alan Menter MD,d April N. Naegeli PhD,b Robert Bissonnette MD MS FAAD FRCPC,e Lyn Guenther MD FRCPC,f John Sullivan MBBS MS,g Kim Meeuwis MD PhD,h Kyoungah See PhD,b and Kristina Callis Duffin MD MSi

aDepartment of Dermatology and Medicine, Division of Rheumatology, Harvard Medical School, Brigham and Women’s Hospital, Boston, MA, USA bEli Lilly and Company, Indianapolis, IN, USA cDepartment of Dermatology, New York Medical College at Metropolitan Hospital, New York, NY, USA dDepartment of Dermatology, Baylor University Medical Center, Dallas, TX, USA eInnovaderm Research, Montreal, QC, Canada fThe Guenther Dermatology Research Centre, London, ON, Canada gDepartment of Medicine, UNSW, Sydney, New South Wales, Australia hDepartment of Dermatology, Radboud University Medical Center, Nijmegen, The Netherlands iDepartment of Dermatology, University of Utah, Salt Lake City, UT, USA

clinical experience with genital psoriasis. Photographs were selected if the reviewer confirmed that the image was a case of genital psoriasis, if the image quality was high (eg, in-focus, well lit, and lacking obstructions of the affected area), and no comorbid conditions (eg, candidiasis) were present that could interfere with sPGA-G assessment. Fifty photographs were selected to represent a full spectrum of severity levels (including “clear”) in both female and male patients. Ten experts in genital psoriasis rated photographs using the sPGA-G. The expert raters were from multiple global regions, including the United States, the European Union, Canada, and Australia. Expert rater specialties and clinical expertise included dermatology, psoriasis, psoriatic arthritis, venereology, and genital dermatology. Seven of ten expert raters had previous experience in clinical outcome measure development. The expert raters had ≥7 years of experience in clinical trials (mean, 20.4 years) and ≥9 years of experience in assessing and diagnosing both psoriasis (mean, 22.6 years) and genital psoriasis (mean,17.9 years). Nineteen photographs (11 male and 8 female) were selected by the expert raters for use in the sPGA-G training and certification materials. Photographs were selected if they (1) satisfied the initial photograph selection criteria (utilizing feedback from the larger group of experts), (2) provided sufficient detail to make an accurate assessment using the sPGA-G, and (3) if the majority (>50%) of expert raters had assigned the same score using the sPGA-G. Final photographs were selected to represent both male and female genital psoriasis across a broad range of severities. Photograph licensing for inclusion in the training materials was completed as required.

sPGA-G Training Modules

The sPGA-G training module included an overview of the sPGA-G scale and guidelines for its use (with a particular emphasis on the importance of erythema), examples of its application in assessing the full range of severity levels for both males and females (as illustrated by patient photographs), and a training examination consisting of 9 photographs (5 male, 4 female). Assessors completed the training examination by providing their best assessment of each photograph using the sPGA-G scale. Assessor scores were compared to the score range assigned by expert raters for the corresponding photograph. If an assessor’s score was within the range assigned by expert raters, it was marked correct. In order to pass training and to become certified to use the sPGA-G in clinical trials, assessors had to assign correct scores for 7 of 9 photographs. Training modules were provided both in-person and online. The in-person training module was delivered as a formal presentation of the training materials followed by the examination. Either a response sheet or an electronic voting response system was used to collect answers. The online training was a narrated computer-based module, identical in content to the in-person training.

Statistical Analysis

Scores from expert raters during photograph selection and from the training examination were analyzed for inter-rater reliability (IRR) using Kendall’s coefficient of concordance (Kendall’s W). Analysis groups included scores from expert raters, in-person assessors, online assessors, and a combined group of the in-person and online assessors. Comparisons between groups were applied using chi-square and Kolmogorov-Smirnov tests comparing the proportion of correct responses and score distribution, respectively. All other values are summarized using descriptive statistics.


Assessment of Genital Psoriasis Using the sPGA-G

Representative examples of female and male genital psoriasis and their associated sPGA-G scores are provided in Figure 1. Figure 1A shows a case of genital psoriasis in a female patient Figure 1with faintly visible erythema and no obvious signs of plaque elevation or scale. This photograph best corresponds to a sPGA-G assessment of 1 (minimal). Figure 1B shows a case of male genital psoriasis characterized by bright red erythema, coarse and adherent scaling, and mild-to-moderate elevation. Overall, this case best corresponds to a sPGA-G score of 4 (severe).

Evaluation of sPGA-G Reliability

Results from expert rater assessments of 19 photographs included in the sPGA-G assessor training module are provided in Table 2. A total of 95 clinician assessors participated in either an in-person (n=28) or online (n=67) standardized training module for the sPGA-G scale. For the in-person training, all assessors (28, 100%) passed the training module on their first attempt: 19 (67.9%) passed with 9/9 (100%) correct, 8 (28.6%) passed with 8/9 (88.9%) correct, and 1 (3.6%) passed with 7/9 (78%) correct. In the online training module, 66 (98.5%) completed the examination. Of those who completed the training examination 64 (97.0%) passed on the first attempt: 31 (47.0%) passed with 9/9 correct, 27 (40.9%) passed with 8/9 correct, and 6 (9.1%) passed with 7/9 correct. Two (3.0%) assessors did not pass the training module on the first attempt (Scores: 5/9 and 6/9 correct). After reviewing the training module a second time, both passed on a second attempt with 9/9 correct. One assessor passed the training module on the first attempt with 7/9 correct but did not provide an answer for one of the two questions marked incorrect. Overall, IRR was high within each analysis group as determined by Kendall’s coefficient of concordance (Kendall’s W). For the expert raters, the Kendall’s W was 0.856 (P<0.0001). For inperson and online assessors, Kendall’s W was 0.822 (P<0.0001) and 0.678 (P<0.0001), respectively. For the combined group of all assessors (online and in-person), Kendall’s W was 0.714 (P<0.0001). Variability was low when comparing the proportion of correct responses (Chi Square) and the distribution of scores (Kolmogorov-Smirnov) between assessor groups (Table 3).


Genital psoriasis is a common feature of patients with plaque psoriasis associated with a significant reduction in quality of life, self-esteem, and sexual health compared to psoriasis patients without genital involvement.5,8,16 Despite its prevalence and burden, genital psoriasis is frequently misdiagnosed or left untreated because of either insufficient communication between health care providers (HCPs) and patients or a lack of routine examination of genital psoriasis by HCPs.7,9,13 The erythematous presentation of genital psoriasis can also contribute to its misidentification as atopic dermatitis, candidiasis, tinea, or sexually transmitted diseases.3,14 Clinical outcome measures, such as the Psoriasis Area and Severity Index (PASI) and the Static Physician’s Global Assessment (sPGA) assess overall psoriasis severity and are routinely used as primary or secondary endpoints in clinical trials.17-19 However, there have been no large scale clinical trials for genital psoriasis, with tools to measure its severity being limited. Those tools that do exist20-22 have not been widely used or ap- propriately validated. Currently, the most well established clinical outcome measure for genital psoriasis is the modified genital PASI (mGPASI), derived from the overall PASI scale.5,15 However, the mGPASI requires assessors to determine the percentage of involvement of the genital area, which may be challenging given the small body surface involved (approximately 1% of the overall body surface).23 In addition, the mGPASI does not account for the predominantly erythematous presentation of genital psoriatic lesions. Moreover, regulatory agencies including the FDA and the European Table 2